New insights are needed in order for parents and practitioners to deal more effectively with juvenile disruptive behavior, delinquency, substance use and their co-morbid conditions. Longitudinal studies are one of the best tools to generate new knowledge about these vexing problems. The PHYS, now in its fifth year with it data collection from target boys, their parents, and their teachers, has achieved a high cooperation rate. The proposal aims at building a data base relevant for optimizing future preventive interventions. For that purpose the study proposes the continued follow-up of 1,009 subjects for another five years. A first aim is to examine the developmental course and prevalence of disruptive and antisocial behavior from ages 7 to 20, including the documentation of the sequence of onsets of problem behaviors (and the late onset of such behaviors), trace developmental progressions in disruptive behavior, examine long-term sequelae, and identify developmental sequences leading to cessation of disruptive behavior. A second aim is to study the influence of co-morbid conditions (attention-deficit/hyperactivity, anxiety, depression, substance use, and learning problems) on the course and outcome of juvenile disruptive behavior. A third aim addresses risk and protective factors relevant for the etiology of disruptive behavior, and examines the degree of specificity of such factors for different disorders and co- morbid conditions. The study measures a variety of risk and potential protective factors, the stability and change of these factors as they are likely to affect the development of different manifestations of disruptive behavior over time.Analytic aims are to narrow down those risk factors which can best explain different developmental processes, such as initiation, escalation, and desistance, and which can best account for individual difference in subjects' traveling on different pathways toward antisocial behavior. A fourth aim is to analyze caretaker's and subject's identification, selection, and utilization of services for disruptive problems an co-morbidities. Because of the repeated measurements of the same subjects over time, it is possible to examine co-variation between independent and dependent variables over critical periods in children's lives. Analyses will make extensive use of data collected over the past five years and, together with the new data, will form the basis of analytic strategies geared at generating new knowledge to optimize future interventions, such as the identification of developmental pathways, the timing of risk factors, the interaction between these factors, and the identification of protective factors potentially amenable for prevention.